ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Quercetin Benefits for Heart Health and Cancer Prevention

Updated on January 2, 2013
The chemical structure of the polyphenol flavonoid known as quercetin. Plants make other types of flavonoids that are also beneficial to health.
The chemical structure of the polyphenol flavonoid known as quercetin. Plants make other types of flavonoids that are also beneficial to health. | Source

What is Quercitin?

Quercetin is a yellow pigment found in plants that is sometimes used as a supplement to improve or prevent various health conditions. It is in a group of common plant chemicals called flavonoids which are found in many fruits and vegetables, and even in dark chocolate. There are four major groups: isoflavones, flavones, anthocyanadins and flavanols. Flavonoids are also called polyphenols because of their chemical structure.

Quercetin acts as an antioxidant in the body, much in the same way that vitamins A, C and E work. These antioxidants supplement some of the body's enzymes that protect it from being damaged by free radicals that are generated in the body from natural processes, the decomposition of fats and exposure to environmental pollutants.

Quercetin also has other beneficial physiological effects, which I cover below. There are specific sections on heart disease and cancer, and, other diseases which appear to benefit from taking daily dosages. These diseases are listed in the section immediately below. Quercetin dosage rates are also covered for diseases where substantial research has been completed.

Benefits of Quercetin

Quercetin combines with and neutralizes free radicals of oxygen and nitrogen. These free radicals damage fats and proteins in the body, modifying their function. A balance of antioxidants in the body help counteract the production of free radicals that are made by various internal physiological processes. A balance of the two helps prevent what is called oxidative stress, leading to many disease conditions related to aging like inflammatory diseases, cancer and the heart condition known as artherosclerosis. A list of some diseases related to free-radical damage which may benefit from quercetin supplementation follows:

  • rheumatoid arthritis
  • adult respiratory disorders like asthma and COPD
  • lupus erythematous
  • stroke
  • vasculitis
  • intestinal ischemia
  • gastric ulcers
  • preeclampsia
  • prostatis - inflammation of the prostate glands
  • hypertension - high blood pressure
  • high LDL cholesterol
  • Alzheimer's disease
  • muscular dystrophy
  • glomerulonephritis - inflammation of the small blood vessels in the kidneys
  • interstitial cystitis - inflammation of the bladder

Quercetin Benefits for Heart Health

Artherosclerosis Prevention. Quercetin is thought to act through the same mechanism as vitamins E and A in preventing the oxidation of low-density lipoproteins (LDL). Endothelial cells, smooth muscle cells and macrophages in the blood vessels can all release hydroxyl (OH) free radicals to cause lipid oxidation. Oxidation of the lipids in LDL is believed to be an important factor in plaque formation in atherosclerosis, or hardening of the arteries. The presence of these antioxidants also prevents direct damage of endothelial cells by oxidized LDL, the cells which line the inside part of the blood vessel.

Prevention of inflammation. Some research indicates that quercetin may have benefit for reducing cardiovascular disease in people who appear to be at low risk for having it. This mechanism appears to be through its role in reducing inflammation markers like C-reactive protein (Wolfgang, 2001).

Other mechanisms. Quercetin also appears to increase the diameter of coronary blood vessels, thus increasing blood flow (Kaur, 2007). This process is called vasodilation. Additional research indicates that two glasses of red wine may have enough quercetin to dissolve clots (Boosye, 2007).

(Note that references in parentheses are listed below).

Quercetin Benefits for Cancer Prevention

Free radicals can directly cause protein and DNA damage; and, they can activate carcinogens. DNA damage can lead to altered DNA function and mutations. Antioxidants like quercetin and beta-carotene (vitamin A) directly scavenge free radical molecules.

Laboratory tests indicate a positive effect of quercetin against leukemia, squamous cell carcinoma, and cancers of the brain, rectum, colon, ovaries and breast. In these cases, it prevents the proliferation of cancerous cells. Limited study results with humans indicate that supplements of curcumin plus quercetin showed positive results with colon cancer patients (Meschino, 2006).

Quercetin Dosage

Therapeutic dosages range from 200 to 400 milligrams, taken 3 times daily. There are no established dosages for either heart disease or cancer, but these rates have been found to be effective with prostatitis and interstitial cystitis. There is no evidence that these dosage rates will cause cancer, but some doctors do not recommend combining antioxidants with chemotherapy.

Bromelain has been shown to increase the antioxidant activity of quercetin, when given in equal doses. Quercetin molecules that are within fruits and vegetables are attached to complex sugar molecules that help intestinal absorption, so eat your fruits and vegetables if you don't have access to bromelain and quercetin supplements.

Quercetin doesn't remain in the body long. It has been observed to stay in the body from 8 to 28 hours. As with all antioxidant molecules, it has a short half-life within the body. This is why it is necessary to keep taking antioxidants on a daily basis to enjoy their benefits.

Natural dietary sources high in quercetin include red wine, grapefruit, onions, apples, black tea. Smaller amounts are found in leafy green vegetables and beans. Here are the amounts in several common foods:

Foods and Beverages with High Quercetin Content

milligrams per 100 grams
Apple (not peeled)
Black currant
Onion, white (yellow has more)
Red tomato
milligrams per 100 milliliters
Tea, black
Tea, green
Tea, oolong
Tomato juice
Red wine
Data from the first reference listed below in the Further Reading section. Note that quercetin content increased with the maturity of the fruit or vegetable, but it (generally) decreases with storage. More are listed below with >1 mg per serving.

Foods with Greater Than 1 mg per Serving

Apricots, blackberries, cherries, grapes, plums, raspberries, green beans, celery, collard greens, kale, spinach, buckwheat and kasha.

Summary: To Take or Not to Take?

So, are the benefits of quercetin real or speculation? At the moment, for heart disease and cancer, it seems that there is at least encouraging evidence for the use of quercetin supplements. The strongest published evidence for its use is with prostatitis and interstitial cystitis.

Since this supplement has significant promise, and that is classified as GRAS, or generally recognized as safe, its use as a supplement in other diseases that are affected by free radicals and inflammation seems justified. However, to receive the therapeutic benefits, it appears you can't get there by just eating your fruits and vegetables. Supplements are needed to reach the levels required for disease abatement, about 1,000 to 1,200 mg per day.

So, if you are over 60 years of age, or at high risk for any of the disease conditions listed above, preventative supplementation may be beneficial. But, don't forget to have a balanced diet, exercise and eat your fruits and vegetables - things that we all know are helpful for living a long and healthy life.

For Further Reading

Aherne, S.A., and O'Brien, N. M. 2002. Dietary flavonols: chemistry, food content, and metabolism. Nutrition 2002;18:75-81.

Anonymous. 2011. Quercetin. University of Maryland Medical Center.

Booyse, F.M. et al. 2007. Mechanism by which alcohol and wine polyphenols affect coronary heart disease risk. Annals of Epidemiology Supplement 17:S24-31.

Kaur G., et al. 2007. Effect of wine phenolics on cytokine- induced C-reactive protein expression. J Thromb Haemost 5:1309-1317.

Lobo, V., et al. 2010. Free radicals, antioxidants and functional foods: Impact on human health. Pharmocognosy Reviews 4: 118-126.

Meschino, J. 2006. Quercetin supplementation may reduce risk of colon cancer. Dynamic Chiropractic 24:50,58,60.

Wolfgang, K. 2001. Inflammation and coronary heart disease: An overview. Cardiology in Review 9:31-35.



    0 of 8192 characters used
    Post Comment
    • shiningirisheyes profile image

      Shining Irish Eyes 

      7 years ago from Upstate, New York

      Thanks for providing me with a well-informed and well-researched article. I had never heard of Quercetin before reading this.

      Very good job with this one. Voting up


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)